The most common and most likely answer to this crossword clue is the 7 letter word COWERED
I've seen this crossword clue in The Daily Telegraph
C
O
W
E
R
E
D
Buddy explains!

The straight part
We know that "shrank back" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shrank back = cowered.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does COWERED mean?
COWERED verb- To crouch or cringe, or to avoid or shy away from something, in fear.
- To crouch in general.
- To cause to cower; to frighten into submission.
- To cherish with care.